Ctjet netto



(No Model.)

O. N ETTO. rnoczss OF MAKING ALUMINIUM.

Patented July 8, 1890.

UNITED STATES PATENT OFFICE.

CURT NETTO, OF DRESDEN, GERMANY.

PROCESS OF MAKING ALUMINIUM.

SPECIFICATION forming part of Letters Patent No. 431,912, dated July 8,1890.

Application filed July 21,1887. Serial No. 244,861. (No specimens.)Patented in England March 21, 1887, No.4,228; in Germany March26,1887,N0. 45,198; in Belgium March 26, 1887, No. 76,860; in FranceMarch 26, 1887, No.182,464,' in Norway June 14, 1887,110. 668: in SwedenJune 14, 1887,1510. 1,206;in Luxemburg June 15, 1887,1510. 854 in ItalyJune 30,1887, XLIII, 232,XXI, 21,838 in Spain August 24, 1887,1To.7,108, and in Austria-Hungary November 29,1888, No. 21,211 and To allwhom, it may concern:

Be it known that I, CURT NETTO, engineer, a subject of the King ofSaxony, residing at Dresden, Saxony, German Empire, have inventedcertain new and useful Improvements in the Process of Making Aluminium,(for which I have obtained Letters Patent as follows: in GermanyMai-ch26, 1887, No. 15,198; in Belgium March 26, 1887, No. 76,860; inFrance March 26,1887, No. 182,464, and June 9, 1887, N0.182,4:64:; inGreat Britain March 21, 1887, No. 4,228; in Italy June 30, 1887, No.XLIII, 232, XXI, 21,838; in Luxemburg June 15, 1887, No. 854; in NorwayJune 14, 1887, No. 668 in Austria-Hungary November 29, 1888, No. 21,211,and No. 39,313; in Sweden June 14, 1887, No. 1,206, and in Spain August2 1, 1887 No. 7,108); andI do hereby declare the following to beafull,clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use thesame, reference being had to the accompanying drawings, and to lettersof reference marked thereon, which form a part of this specification, inwhich- Figurel is a plan view, partiallyin section, of the dipping-rodwith a piece of potassium thereon. Fig. 2 is a side, and Fig. 3 a top,view of the ladle or cover. Fig. 4 is a vertical sectional view of acrucible with the dipping-rod and ladle therein; and Fig. 5, ahorizontal sectional View of the same, taken on the line A B of Fig. 4.

The present invention has relation to processes for the manufacture ofaluminium; and it consists in a process for manufacturing aluminium fromcryolite by means of the alkaline metals, asherein after fullydescribed,and specifically claimed.

As early as 1855 Percy, Rose, WVoehler, and Deville proposed methods ofmanufacturing aluminium from cryolite by means of sodium. Though thismineral is found in nature in great quantities, it has not beensufficiently employed for the manufacture 011 a commercial scale ofaluminium, for the reason that the chloride of aluminium is so(llfllGlllt to produce that its double combination with chloride ofsodium has generally been used. The reason for this is that thereduction of cryolite by means of alkaline metals is subject to theobjection that its melting-point, being even in the presence of asuitable flux between 750 and 800 centigrade, surpasses theevaporatingpoint of sodium and also of potassium. It, therefore,

as in the Deville process, a charge of cryolite flux and alkaline metalsis heated,the better part of the latter escapes in vapor before thetemperature is reached necessary for the melting or the reduction of thecryolite. The profit with reference to the. sodium employed is of coursethereby much reduced. This Deville himself corroborates by the followingsentence: I have verified all of Mr. Roses observations, and I agreewith him concerning the return of metal, which I have always found verysmall. (Richards, manufacturer of aluminium, Philadelphia, 1887, pages119 and 120.)

The object of my invention is to effect the melting of the cryolitecontrary to the De ville process, not in the presence of the alkalinemetal, but (and this is the characteristic point of the invention) tomelt the cryolite to be decomposed and then to add the transferringmetal. This process offers, also, the great advantage that aluminium maybe obtained on a large scale from cryolite by means of sodium, and thatthe great loss of this metal by evaporation, now inevitable, is avoided.

The process can be carried into effect in the following manner: Thecryolite, together with the flux, is melted in a crucible, and a pieceof solid sodium or potassium is suddenly introduced and forced to thebottom of the crucible by means of an iron rod, to which the metal hasbeen attached. The alkaline metal being excluded from the air andsurrounded by the molten cryolite, which is now at the temperature ofreduction of alun1inium, it cannot burn. It will, on the contrary,producean immediate change or reduction of the fluoride of aluminiumcontained in a latent state in the cryolite. The introduction of thealkaline metal into the molten mass is not dangerous when care has beentaken that it is quite dry, free of inner hollow. spaces, and ofadhering or other particles of carburet of hydrogen. When the change isfinished, as soon as the mass commences to flow more quietly thecontents of the crucible are thrown into a suitable conical moldnarrowing toward the bottom, where they are allowed to cool. Thereuponthe mold is turned upside down, and the regulus of aluminium, havinggathered at the bottom, is separated from the adhering scoria bystriking it with a hammer. Instead of effecting the fusion of thecryolite mixed with flux (it is best to take one hundred parts, byweight, of cryolite to one hundred parts of chloride of sodium as flux)and the reduction in the same vessel, I can effect the melting in oneand the reduction in a separate vessel. In this case I can make use ofmelting devices which will allow the melting of great quantities ofcryolite, thereby securing a great economy in fuel, crucibles, andlabor. To effect this I can make use of reverberatory furnaces, on thebottom of which the charge of cryolite is melted, after having coveredit with a material free from silicon. thin it is drawn off into a vesselsimilar to a casting-pan having an inside lining of basic material, andmetallic sodium or potassium in the form of a cone attached to an ironrod is plunged to the bottom, whereupon a lively reaction takes place,considerable heat being developed, so that the mass without any furtherheating reaches atemperature necessary to the completion of thereduction. In a few seconds the alkaline metal is consumed, and thisoperation is repeated with new quantities of sodium or potassium untilthe theoretical quantity (to one hundred parts, by weight, of cryoliteabout thirty-three parts of sodium or fifty-six parts of potassium) isadded. WVhen the alkaline metal is not submerged fast enough in the bathor in the molten cryolite, some of the melting alkaline metal beingspecifically lighter, comes to the surface, where it would uselesslyburn away in contact with the air and be lost. In this case I make useAs soon as the mass is liquid and' of a suitable dipper consisting of aconcave iron head of a somewhat smaller diameter than that of thereducing-vessel. This head is provided in the center of its convex sidewith an iron rod, so that it may be, after the introduction of thealkaline metal, plunged into the bath to any depth with its concave sidedownward in order to press down the coming to the surface.

As soon as the proper quantity of sodium or of potassium is introducedinto the molten cryolite the contents of the reducing-vessel are throwninto a reservoir, where it can cool and wherein the produced aluminiumgathers in a large mass. The alkaline metal may be also introduced in aliquid state into the previously-melted mass of cyolite withoutdeparting from the spirit of my invention, or an alloy of sodium andpotassium can be employed in place of using these metals separately.

As the liquid alkaline metal could not be carried to the bottom of themolten mass by means of a rod, other means must be employed to mix thespecifically-lighter alkaline metal with the mass of cryolite. For thispurpose I can introduce the liquid alkaline metal into the bath near thebottom of the reducing metal by means of pressure or mix it by stirring,the most important point of the process being that the cryolite isheated or melted and is afterward while in a liquid state suddenly mixedwith the alkaline metal.

Having described my invention, I claim- The herein-described process forthe manufacture of aluminium from cryolite by the use of the alkalinemetals, such as potassium or sodium, which consists in first melting thecryolite with its flux and then suddenly introducing the alkaline metalor metals into the molten mass, substantially as described. In testimonywhereof I affix my signature in presence of two witnesses.

OURT NETTO.

\Vitnesses:

ROBT. M. HOOPER, PIERRE ERNEST EIPISY.

melting alkaline'metal and to prevent it from

